FIG. 1 of the accompanying drawings illustrates a simplified example wireless mesh communications network which provides a multipath connection between a base network 14 and a cell 16 of a cellular wireless telecommunications network. The wireless mesh network comprises a plurality of network nodes 10 interconnected by bidirectional wireless communications links 12. The network nodes 10 operate to communicate with one another for the transfer of communications data therebetween. This type of network is known as a “mesh” network because of the multiple connections between network nodes that defines a mesh of communications links 12. One particular mesh network makes use of wireless communications links that operate in the millimetre waveband, for example around 60 GHz.
Such a mesh network is suitable for providing a cell 16 of a cellular wireless telecommunications network with a connection to a fibre optic network connection 15 for communication with the base network 14. The cell 16 is operable to communicate with a plurality of mobile communications devices in accordance with well-known standards and techniques. For example, the Long Term Evolution (LTE) standard defines one suitable cellular communications technique.
In the example of FIG. 1, a first network node 101 is connected with a base network 14 using an optical connection 15. The connection between the first network node 101 and the base network 14 may be provided by any suitable connection technology. The mesh network provides a connection between the first network node 101 and a second network node 102. The second network node is connected with a cell station that defines a cell 16 of a cellular communications network. The mesh network provides communication for data from the cell 16 to other devices within or without the mesh network. Such a mesh network is known as a “backhaul” network.
In order for the cellular network to operate correctly, it is important that the cells of the network maintain a synchronous clock signal. Accordingly, it is necessary for the individual cells to maintain a clock signal that is synchronised with a master clock signal for the cellular network concerned. In addition, it is desirable for the individual network nodes to have access to a master reference clock signal in order that mobile phone cell to cell interference and signal management can be completed accurately.
One of the challenges associated with implementing a mesh network, particularly a wireless mesh network over a wide area, is that of maintaining such accurate and synchronised clock signals over the network. However, previously-considered network techniques for adjusting clock signal synchronisation are not ideally suited to wireless mesh networks, since the nature of multi-hop wireless connections mean that the clock signals can quickly become asynchronous.
Accordingly, it is desirable to provide a new technique that seeks to address the drawbacks of previously-considered clock synchronisation techniques.